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How to Replace a Cadillac's Catalytic Converter

The purpose of the catalytic converter is to take the harmful gases out of the exhaust system and convert them into something that can be safely emitted into the atmosphere. The converter is located in the exhaust system between the muffler and the engine. They can become damaged through overheating or road debris. At some point, you will need to replace your Cadillac’s catalytic converter.

Here are some symptoms of a failing catalytic converter:


If your engine misfires, it can cause overheating in the converter. This can come from a rich fuel mix. The raw fuel goes into the converter where it is ignited. This can cause the catalyst compounds to get too hot and melt.


Your engine can stop breathing if exhaust is trapped in front of the catalyst. That can cause the performance to suffer due to an increase in back pressure that causes your car to stall. When you press the accelerator, you won't get a response.

Fuel Economy

You will notice a decline in fuel efficiency. A failing converter can cause the engine to use more gas.

Exhaust System

There may be a problem with the fuel system that can cause the converter to fail. You will notice a restrictive exhaust system, which means that the catalyst materials are melting.


You can test the catalytic converter if you have a carburetor. It takes two people to do the test. Remove the air cleaner. Put a bright light at the carburetor intake. Look over the carburetor to where you see the shining light and rev up the engine. You are looking for suspended fuel vapor in the light. If you see this, then the catalytic converter is clogged.


You can also take out the oxygen sensors for a moment, and if you find that the performance is altered, the catalytic convertor is clogged and failing.


Sometimes, there can be contamination in the catalytic converter from things like antifreeze or oil. If this happens, you may notice a higher level of carbon being emitted. You must replace the catalytic converter as soon as possible or risk exhaust system damage.

Back Pressure

Back pressure is a problem associated with blocked catalytic converters. They can get backed up with dirt, debris, soot and exhaust products. You can test for this by screwing a pressure gauge into the hole on the catalytic converter where the oxygen sensor goes. A normal pressure reading will be 1.25 psi or less when you have the engine revved up to 2,000 RPMs. Congestion will cause the pressure to build.

Mallet Test

On an old converter, take a rubber mallet and give the converter a firm whack. Any rattling sounds mean that the metallic catalyst has begun to crumble or corrode.

Removing Your Cadillac’s Catalytic Converter


  • Oxygen sensor socket
  • Ratchet wrench
  • Jack and jack stands
  • Replacement catalytic converter
  • Penetrating oil

Start by parking your vehicle on a flat, dry surface. Let the exhaust cool down. Consult your owner’s manual on how to jack up your car. Never jack up a vehicle on an uneven surface or use unapproved jack stands to hold it up.

  1. Jack up your Cadillac.
  2. Make sure your exhaust is cool before you start to work on it. Put on mechanic’s gloves. Test it by running your hand lightly against the exhaust tube. If you do not feel any heat, carefully test it with your bare hands.
  3. On your back, slide yourself under your car and find the exhaust tubes. They run all the way to the rear of the car. You should see a small round or rectangular box in the center of your exhaust system. It should bolt in unless it has been worked on in the past and is welded on. If that is the case, then you will need to either use a sawzall to remove it and weld it back into place or take it to a professional.
  4. Take the oxygen sensor off the converter. You may have more than one. They can be removed with a sensor socket and ratchet wrench. Move it out of the way, so you can continue to remove the converter.
  5. The bolts that hold the converter on may be rusted or corroded, so you may need to apply some penetrating oil and allow it to run into the bolt holes before you try to get the bolts off. It may take a couple of minutes.
  6. Start at the back bolts and loosen them first. Next, move to the front bolts, so that they are all loose. Remove them from back to front, and take the converter off.
  7. If the converter is welded in, then you need to cut it out. Cut along the weld lines and remove it. You may need to knock it with a hammer to get it loose if does not drop out easily. Do not hit so hard that you damage any of the pipes or exhaust system parts.

Installing a New Converter

If you received installation instructions with your new converter, then follow those. Otherwise, here are the instructions for installing the new catalytic converter.

  1. Install the new gaskets that came with your converter. This gives the converter a snug fit.
  2. Place the catalytic converter in the right position and make sure that you have it set in the right direction with the correct side down.
  3. Use your fingers to tighten the nuts to the bolts. Finish bolting it down front to back once you have it seated where it belongs. You want a good connection, so make sure that you have them very tight.
  4. If your converter is a weld-in model, then use your MIG welder to join the converter to the exhaust pipes at either end. This may require you to flare the ends to get them to fit. You may need an extension pipe if one is not long enough. Make sure your welds are cool before going to the next step.
  5. Replace the oxygen sensor(s). Make sure that the wiring is not damaged or frayed. Replace any substandard wiring.
  6. Check over your work to ensure that bolts are tight and welds are complete.

Test for Leaks

Now that you have installed a new catalytic converter, you want to check for exhaust leaks. An exhaust leak can cause damage to other parts and reduce your fuel mileage.

You can test your exhaust in a couple of ways.

  1. Listen for louder than normal sounds when you are driving
  2. Jack up your car. Put it in Park. Move a lit candle along the exhaust tubing. The flame will waver or blow out if there is a leak.

The new catalytic converter should have your Cadillac performing like new, but if you find that you are still having trouble, or you are not sure if you need a new converter, then be sure to seek assistance from your local Cadillac dealership.